Update Python c bindings to correctly find shared library files

[rdaly525]

Update Python c bindings to correctly find shared library files

[leonardt]

Task 1 finished in #29

[leonardt]

I imagine the Python interface to look something like

ctx = Context()
stdlib = ctx.load_library("stdlib")

To do this, it could dispatch on the argument to load_library and call the correct function coreir_stdlib.CoreIRLoadLibrary_stdlib(ctx) but either:

• The coreir library (e.g. stdlib) defines an extern C function and uses the coreir-c opaque types, or
• The library registers itself with the C-api which holds a map between strings to library function pointers and provides a C-api function coreir_lib.LoadLibrary(ctx, name) which handles converting the Namespace* and Context* between cpp and opaque types.

[rdaly525]

@leonardt In regards to #2, how does the library register itself with the C-api? I think it would still necessarily involve writing an extern C function per library. Unless I am misunderstanding something...

That being said, it would be cool to be able to register library functions which would mean no need for a specific function name standard.

[rdaly525]

@leonardt I just pushed to the clibfix branch (off of libreorg) the addition of the C stdlib api. There are three TODOs (one in lib/libs/stdlib.cpp, two in include/coreir-libs/stdlib.h)

It would be awesome if you could make macros (defined in include/coreir.h) that would macrofy each of the 3 TODOs.

Also now that we have the C api for the libs, you can add them to the python bindings

[leonardt]

README updated -- link
@rdaly525 Should I submit a PR for this branch or are there other fixes pending? I'll wait to close this issue until we merge the branch.